Parts of speech are classes of words that perform different functions in the sentence. They are like members of a family, each member performing his assigned function for the smooth running of the entire family. And as every family has its own number of members, so also every language has its own number of parts of speech.
The ancient Greek Language, for example, had eight distinct parts of speech noun, verb, participle, article, pronoun, preposition, adverb, and conjunction. Latin had seven parts of speech (noun, pronoun, verb, adverb, preposition, conjunction and participle). But Roman grammarians, in a bid to raise their language to the imposing height of Greek, introduced the interjection to make their parts of speech eight. They used the interjection to replace the article which did not exist in their language. In the same vein, English language ought to have seven parts but after a protracted debate by English grammarians on whether they should retain the seven (noun, pronoun, verb, adverb, preposition, conjunction, and adjective), or increase to eight by adding the interjection, or further increase to ten by adding both the Greek article and the Latin participle, they, eager to make their language as prestigious as Greek and Latin, agreed in 1850 to adopt the classical eight parts of speech, following Joseph Priestly’s 18th century classification: noun, pronoun, verb, adverb, adjective, preposition, conjunction, and interjection. However, the interjection cannot pass for a part of speech because it has no grammatical function associated with it. Hence, we can safely say that we have seven and not eight functional parts of speech in English language.
Contemporary grammarians have criticized the classification of English words into eight parts of speech. They argue that, even though the eight parts of speech have been generally accepted, there are many inadequacies in the classification. This is because the criteria used in the classification are often found to be irregular, resulting in arbitrary grouping of words. As a result, it is difficult to find all the words classified as one part of speech being the same. In other words, all nouns, for example, do not possess a single characteristic since, in most cases, the basis of definition slides from meaning to function. Many grammarians, therefore, have suggested that words should be classified based on their functions in a particular sentence, and not according to their forms or meanings.
All the words used in the English language belong to the eight parts of speech. The part of speech of a word is determined by the position and by the function that word performs in the sentence. It is therefore necessary to use a word in a sentence as well as know the duty it performs in the sentence before we can give it an appropriate name as a part of speech. In modern grammar, these parts of speech are referred to as WORD or FORM CLASSES, to which are two more parts: Lexical verbs and Auxiliary verbs.
The ten WORD or FORM CLASSES are divided into two broad categories; they are:
- Major (or open) Word Classes: Words in this category carry the bulk of the meaning of a sentence. They are referred to as “open” because it is only to them that new words can be added. Words in this category are also called “content” or “lexical” words. Others are nouns, adjectives, and adverbs.
- Minor (or closed) Word classes: The structural role of words in Minor word classes is usually more important than their meaning. Words in this category are regarded as “closed” because no new words can be added. Unlike words in the major word classes, the total number of words in the minor word classes could be listed; they are: auxiliary verbs, determiners (the, this), Pronouns, Prepositions, Conjunctions, and Interjections.